Of course, the audience knows that Amanda has kept Peller alive so he can crack into Birkhoff's (aka "Shadow Walker") ShadowNet. Infiltrate Nikita's network and use the father against his own son? Amanda has reached new heights of cruelty. In the promo for "Pay-Off" below, we get a glimpse of Peller, what looks to be a missile, and Amanda and Nikita (Maggie Q) facing off. Stanford adds, "Birkhoff has an undercover moment out in the field."

Here's what else Stanford has to say about working with Nelson, his years on Nikita and what's next:

When you first read the script for the last episode when Birkhoff was acting all suspicious, were you nervous that he might actually be a traitor or a double? Aaron Stanford: Well, I wasn't because they told me ahead of time what was going to happen. Besides, I was pretty sure they weren't going to do that because they didn't want to feel that collective hate and wrath from their audience because people really seem to like Birkhoff. I don't think they were in any hurry to kill him off or make him a turncoat or anything like that.

You're right. Your character is a fan favorite. When I did a poll at the beginning of the season asking which cast member could die, fans were saying, "Please, anyone but Birkhoff!" What do you think is the appeal of this character? Stanford:[Laughs] It's nice to feel the love. I think the appeal in general of the Birkhoff character is that he's the way in for the audience. He's the most human of all of them as opposed to superhuman like Nikita or Michael (Shane West). He's somebody that people can really relate to. I think people cast themselves in the Birkhoff role. That's why they like him. And he does have some good one-liners.

Speaking of, Nikita has a great line when she learns of his true identity: "You changed your name from Lionel to Seymour?" Really, do you know why Birkhoff would do that?Stanford:[Laughs] Yeah, that's a big favorite for everybody. We really didn't get into that. I think my response to that is: Don't ask. Who could possibly think of a legitimate reason for that?

Were you excited to learn more about Birkhoff's past? Stanford: Yes, I was happy to get into his past. I've been anxious to do that for the past three seasons now. They never got into it and they kept thinking they would be able to do it, but just not getting to it. So it's nice that in the final season there's finally that pay-off of backstory for Birkhoff. How psyched were you to find out that Judd Nelson would play your dad?Stanford: Oh man! I can't even begin to tell you. I had a fangasm when I found out about that. I worshiped Judd Nelson in The Breakfast Clubgrowing up. I must've seen that movie 100 times. I memorized every single one of his lines and mannerisms and modeled myself after him. He was just a really big childhood hero. Getting a chance to work with him was very, very cool. And you get in a fight with him! Was that actually you two or stunt people?Stanford: That was us because it wasn't very involved. If I remember correctly it was like a shove, a disarm and a couple of quick strikes. We both managed that on our own. Judd was remarkably spry for a man of his age. He can hold his own. Even if all goes well and they reunite, Birkhoff and his dad won't ever really be buddy-buddy, right?Stanford: Well, never say never. I think that were they to reunite, the idea is that both of them have grown up a little bit since the initial split. They both have a lot of regrets about the way they behaved toward each other.Yes, well, faking your own death is pretty extreme.Stanford: It's pretty extreme, but to be fair, my father was an extreme d---, so the punishment fits the crime!

This continues Birkhoff's trajectory of being more in the field, a little less computery stuff.Stanford: Right and the headquarters are on the move this season anyway. That element was a new wrinkle. And things are sort of unraveling in the last season. Everyone is sort of changing roles. People are behaving in different manners because everyone's arc is coming to an end. So everyone's stepping out of the normal roles we know them in and exploring new territory.

Let's assume that Birkhoff and Sonya live. What would you want for them in the future?Stanford: Obviously I'd want them to stay together. I'd like them to remain a couple and be true to themselves. One would hope. Eventually, the world could use more Birkhoffs and Sonyas for sure. So hopefully they stay together and stay true to themselves and spread the message of freedom through the internet.

In doing Nikita these past few years, what have you added to your skill set?Stanford: I absolutely know how to sit in front of a computer screen, that's for sure. I think that with Birkhoff's character I really learned how to imbue very, very dry and technical exposition with life. How to make a piece of very, very functional dialogue entertaining.

Looking back at all four seasons, do you have a favorite episode?Stanford: My favorite episode is "Shadow Walker" obviously. That was the real episode where Birkhoff got a chance to really stretch. There was real opportunity to change and grow within that episode. Usually, in a lot of episodes, Birkhoff is just a device. He needs to communicate information to the audience through exposition and provide a bit of comic relief through his one-liners. So any episode where I really actually got a chance to really get in there and get something to sink my teeth into, I was really happy. "Shadow Walker" is the best example of that.

What will you miss the most?Stanford: We did have very good craft services. [Laughs] But I will not miss the winters. With any project, it's always the people, the friendships that you make, the experience that you had working together. When you're done with a job, even if you do stay in contact with certain people, it's never quite the same. It's a unique experience when you're working on a film or a television show together. You're together for 16 hours every day, sometimes six days a week. You're just never going to have that proximity again. So you miss people. But I'm working with Noah on this new show. So the super-friendship continues.Let's talk about that. Is the project 12 Monkeys? What can you tell us about that? Stanford: The show is 12 Monkeys, and I'm playing the role that Bruce Willis played in the original film 12 Monkeys. It is a show about time travel. My character is from a future post-apocalypse and he has been given a mission to go back in time to essentially set things right and stop the apocalypse. No big deal. Noah Bean is playing the ex-boyfriend of the female lead, who is played by Amanda Schull, who was also on Nikita. So it's a big Nikita reunion. He's the one who in a way gets in between the two of us.Will you be working during the holidays?Stanford: We finish [12 Monkeys] before the holidays so I'm not working. I'm going to go to New York City with my girlfriend to go see Ian McKellan and Patrick Stewart do their two plays in rep: Waiting for Godot and No Man's Land. Should be fun.Nikita airs Fridays at 9/8c on The CW.

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